Multiwavelength transmitters have been demonstrated where full monolithic integration of the indium phosphide (InP) optical elements onto a single chip is achieved. For example, a fully monolithically integrated multiwavelength transmitter has been reported by Infinera Corporation of Sunnyvale Calif., USA (“Large-Scale Photonic Integrated Circuits”, Nagarajan et al, IEEE Journal of Selected Topics in Quantum Electronics, Vol 11, 1, pp 50-62, January 2005) where several wavelength source lasers and individual wavelength channel data modulators are combined with an InP arrayed waveguide grating (AWG) on a single chip. A monolithically integrated multiwavelength laser source has also been reported (IEEE Photonics Technology Letters Vol. 6 (9) p. 1082 (1994)) where individual optical gain elements are used for each wavelength channel and the different wavelength outputs are combined with an AWG.
In order to be cost effective, these devices require extremely high production yields of the optical elements in order that all the elements (and the module) function within specification.
This invention, at least in its preferred embodiments, seeks to provide a multiwavelength transmitter which does not require such high production yields.